Portable screening/dosing/mixing plant

ABSTRACT

A high-rate portable self-contained combination screening/dosing/mixing plant is mounted on a single tractor trailer for highway travel in most states without requiring travel escort vehicles. The plant has a nominal capacity of about 100 tons of soil or dirt per hour, and includes an apparatus train for preliminary separation of large objects, hopper storage, uniform feed rate, shredding-pulverization, particle size screening, additive dosing, mixing and conveyance to an elevated position for transfer to a dump truck, bin or pile.

BACKGROUND OF THE INVENTION

This invention relates generally to machines for screening aparticulate, granular or other multi-sized material and treating a sizefraction thereof. More particularly, this invention pertains to portableapparatus useful for soil remediation and the like.

At numerous locations, the ground has been contaminated by accidental ordeliberate application of gasoline, fuel oil, used petroleum products,or various chemicals. In most soil remediation processes, thecontaminated soil is first removed from the ground and separatelytreated to chemically or biochemically remove the contaminant ortransform it into a non-soluble, non-volatile and/or non-offensivematerial. In most of these processes, a remediating additive is to beintroduced and mixed with the contaminated soil.

In one type of process, specialized microorganisms which consume thecontaminant may be introduced or dosed in either solid or a liquid form.

In other remediating processes, various chemical entities may be addedwhich bind with or encapsulate the contaminant. Certain contaminants maybe chemically converted to non-toxic or less toxic substances.

In most cases, the soil must be pulverized into small particles so thatmaterial surfaces are effectively exposed to the additive. In addition,the contaminated soil and additive must be intimately mixed to ensurerapid remediation.

The extent of many contaminated sites requires large quantities of soilto be removed and treated. For example, a 5 acre site contaminated to adepth of 6 feet requires the removal of about 50,000 cubic yards ofmaterial weighing about 40,000 to 100,000 tons, depending upon the typeof soil and moisture content. Economic treatment typically dictates hightreatment rates of 50 or more tons per hour. Thus, a treatment plantoperated at 80 tons per hour will take about 5 months (at 168hours/month up-time) to complete the remediation operation.

Many contamination sites are much smaller, of course, requiring muchless treatment time. Likewise, some contamination sites are ofconsiderably greater extent.

In the past, equipment for performing such large-scale remediation wasmounted on a plurality of trailers or trucks, each separatelytransported to the remediation site. Multiple trailers requiringintermediate process equipment results in higher equipment costs.Significant costs associated with such operations include the use ofmultiple truck drivers. In addition, if oversize trailers are used,escort vehicles may be required, increasing the overall cost of travelbetween operation sites.

The plurality of trailer mounted units also requires considerableon-site assembly time for connecting the trailers with conveyors to forma single operating train. Additional conveyors may be required fortransporting the process material from trailer to trailer, and the plantmay require more ground area than is desirable, i.e. have an excessive"footprint".

One of the factors which must be addressed in designing a treatmenttrain is the change in elevation of the material being treated as itpasses through a treatment step. When the elevation drop is great enoughso that the material cannot be discharged from one treatment stepdirectly into the following step, a conveyor must be used to gain thedesired elevation. Because of the sizeable elevation drop of the "fines"through a screening operation, portable apparatus for screening haverequired an intermediate hopper and conveyor for collecting screenedmaterial and feeding it to a mixer.

A related constraint affects the sizes of the belt conveyors. The angleat which solids may be conveyed upwardly by belt conveyor has arelatively low maximum value. If this value is exceeded, the materialsbeing conveyed may slip backwards and/or fall off the sides of theconveyor belt. At a given angle, the minimum length of a conveyor isproportional to the vertical difference between the inlet and outletelevations.

BRIEF SUMMARY OF THE INVENTION

The primary objective of this invention is to produce a unitary portablemachine which includes apparatus for pulverizing and screening aparticulate material, intimately mixing an additive therewith anddischarging the treated material.

Another objective of the invention is to produce a high-capacityself-contained soil remediation machine which is easily transported to acontamination site.

An additional objective is to produce a high capacity soil remediationmachine which requires no external power source.

A further objective of the invention is a high-rate machine includingapparatus for pulverizing and screening a particulate base material,introducing an additive, and intimately mixing the additive with thebase material, wherein all of the apparatus is mounted on a singleover-the-road trailer of a size and weight for travel without escortvehicles.

An additional objective of the invention is to produce such a machinefor the purpose of soil remediation, wherein a design soil handling rateof about 75 to 100+ tons per hour is adaptably variable to accommodatewidely ranging remediation site sizes and conditions. The cost ofmultiple truck drivers and escorting vehicles is eliminated or reduced.

More particularly, the objective encompasses a portable plant for theremediation of ground material by chemical conversion, chemicalfixation, encapsulation, pH adjustment, solidification,devolatilization, microbial addition and/or other treatment with anadditive material.

To meet a further objective, a unitary portable large-scale plant isproduced which first breaks up and screens a stream of compost substrateor composted organic matter. In the plant, an additive such aswastewater filtercake or lime is then added, and the combination isintimately mixed and continuously discharged to a vehicle, storagecontainer or pile. Oversized materials are rejected from the processstream and separately removed for reprocessing or separate disposal.

The invention is a self-contained portable unitary plant forsize-screening a particulate material, combining and intimately mixingan additive with the screened material, and discharging the mixture.

These and other objects and advantages of the invention will be readilyunderstood by reading the following description in conjunction with theaccompanying figures of the drawings wherein like reference numeralshave been applied to designate like elements throughout the severalviews.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B together form a right side elevation view of a portablescreening/dosing/mixing plant in accordance with an embodiment of theinvention;

FIGS. 2A and 2B together form a top view of a portablescreening/dosing/mixing plant in accordance with an embodiment of theinvention;

FIG. 3 is a front view of a portable screening/dosing/mixing plant inaccordance with an embodiment of the invention;

FIG. 4 is a rear view of a portable screening/dosing/mixing plant inaccordance with an embodiment of the invention; and

FIG. 5 is a cross-sectional plan view through the vibrating screendischarge chute of a portable screening/dosing/mixing plant of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, and particularly to FIG 1A and 1B, aportable, trailer-mounted, self-contained combinationscreening/dosing/mixing plant is depicted which is effective forintimately combining two streams of materials. The plant is useful fore.g., remediation of contaminated soil, production of soil amendmentmaterials, and high rate blending of desired additives with solidparticulate materials.

While the apparatus is known herein as a "screening/dosing/mixing"plant, it is to be understood that the material being processedundergoes other operation steps including grizzly size separation,pulverization, oversize material transport, product transport anddischarge.

As used herein, the term "particulate" refers to any material which isprimarily noncontinuous and largely comprises solid or semi-solidpieces. The particulate material referred to may range from uniformlysized grains, such as sand, to a soil or compost having entities ofwidely varying sizes and compositions, including materials of animal,vegetable and/or mineral origin. Moisture or other liquid may beassociated with the solids. Thus, a contaminated soil may containmineral soils as well as grass and other plant growth. In addition, thesoil may include matter of animal origin.

As shown in FIG. 1, the screening/mixing plant 10 comprises a processtrain 12 for continuously processing a material at a high rate. Theentire process train 12 is mounted on a single trailer 14 capable ofroad transport without accompaniment by escort vehicles.

The train 12 is configured to receive the soil or other particulatematerial in a primary hopper 16 and transport it in a stream from thefront end 18 of the trailer 14 to the rear end 20 thereof, anddischarging the material rearwardly of the trailer 14 at an elevatedposition 22 which is preferably at a height 24 at least 12 feet aboveground level 26.

Following the general order in which materials are processed, FIGS. 1-4show the equipment mounted on the trailer 14 in an operating mode. Theitems of equipment include the primary hopper 16 with a grizzly 28mounted on the hopper inlet 30 for rejecting grossly oversize objects inthe material stream. A belt feeder 32 is mounted below the hopper 16 totransfer a stream of material to a shredder 34 such as a hammer mill.Shredded material is discharged from the shredder 34 to a primary beltconveyor 36 which transports the material upward and rearward to adischarge hood 38. The hood 38 directs the stream of shredded materialto a reverse-mounted single deck vibrating screen 40 which separatesoversize material from the stream and also acts to further reduce thesize of some types of material. Oversize materials are carried away fromthe plant 10 by an oversize cross conveyor 42. Materials of smallparticle size pass through the screen 40 into a discharge chute 44 whichsupplies the inlet end 46 of a mixer 48 comprising a pug mill. Afoldable belt conveyor 50 herein known as an end conveyor is positionedto receive mixed material from the pug mill 48 and convey it to theelevated discharge position 22.

The train 12 also includes means for introducing an additive to thematerial prior to mixing in the pug mill 48. The figures show additiveintroducing means in alternative forms. A pump 52 is shown mounted onthe trailer 14 for introducing a liquid additive through conduit 54 toone or more spray bars 56 placed within the screen discharge chute 44above the mixer 48 (see FIG. 5). Pump 52 has an inlet 60 configured forconnection to a conduit from a tanker truck, not shown, or a separatestationary tank. The pump 52 may be a metering pump for controlling theliquid flow rate, or the flow may be controlled by a separate valve 62in conduit 54.

In another embodiment, an aperture 64 is provided in the screendischarge chute 44 for accepting a screw conveyor 66 with motor 67. Itis to be understood that the screw conveyor 66 may convey additivematerials from any suitable container 58 as shown in FIG. 4. Theadditive container may be a ground-supported hopper, truck, trailer orother container.

If desired, a solid or liquid additive may alternatively be introducedearlier in the train 12, such as into hopper 16, onto primary conveyor36, or onto the vibrating screen 40. If desired, other types ofconveyors may be used for dosing the base material stream with additive.For most additives anticipated for use with this apparatus, thepreferred place of introduction is within the screen discharge chute 44.

The entire process train 12 is configured so that it is supported on atrailer 14 to be pulled by a semi tractor, not shown, and it fits withina size envelope having a length 68 of no more than about 50.5 feet fromkingpin 70 to rearmost wheel axle 72, width 74 no more than about 8 feet5 inches, and height 76 no more than about 13.5 feet. In the illustratedembodiment, the trailer 14 is shown as having an overall length 78 fromkingpin 70 to rearmost surface 80 of approximately 53 feet. With thesedimensions, the plant 10 may be transported on highways in most stateswithout needing escort vehicles. While the figures show the trailer 14with a total of only four rear wheels 88, it is anticipated thatadditional wheels may be required in some instances to meet highway loadrequirements.

As depicted in the figures, the plant 10 is capable of processing up to75-100 tons per hour, or more, of contaminated soil or other particulatematerial by adding to it a remediating material, intimately mixing thetwo streams, and discharging the mixture to a storage bin, vehicle, orother receiving area.

Primary hopper 16 is shown with straight sloping sides 82 and atruncated bottom 84 which opens onto the feeder conveyor or belt feeder32. As depicted, the hopper 16 has a capacity of about 6 to 12 cubicyards (typically about 9 cubic yards), and is supported by frame 86.

The primary hopper 16 has an upper inlet 30 into which raw material suchas contaminated soil is introduced by a conveyor, front end loader, orother machine, not shown. A grizzly 28 is mounted to the hopper inlet 30for removing grossly oversized materials. As shown by comparing FIG. 1Awith FIG. 2A, the grizzly 28 comprises a set of laterally spacedparallel bars 90 placed on edge and joined to form a bar screen. Thegrizzly 28 has an outside frame 94 which is pivotally attached along oneside to the hopper side 82 with hinges 96. The grizzly 28 may beperiodically pivotally raised by hydraulic cylinders 98 to permitoversize materials to slide off. A bar spacing 92 of about 4 inches willremove boulders, stumps, large tree branches and roots, etc. Onlymaterials having a dimension smaller than the bar spacing 92 will passinto the hopper 16. If desired, the grizzly 28 may be mounted at anangle from the horizontal for continuous discharge of grossly oversizeobjects.

As shown in FIG. 1A. the belt feeder 32 is positioned below the hopper16, and comprises an endless belting 100 with end pulleys 102 andclosely spaced idler rollers 104. The belt feeder 32 is configured toprovide a uniform discharge rate from the hopper 16 into shredder orpulverizer 34. The shredder 34 may be of the well-known hammermill typeor other type of pulverizer for breaking up a continuous stream ofmaterial. FIGS. 1A and 2A depict the shredder 34 as a hammermill drivenby a hydraulic motor 108. The shredder 34 must be capable of breaking upclods of hardened earth, earth containing solidified organic matter,and/or small pieces of plant matter. The shredded material is dischargedfrom the shredder enclosure 106 to the primary belt conveyor 36.

As illustrated, primary belt conveyor 36 includes a framework 110, areceiving trough 112, endless belting 114 which encircles a tail endpulley 116 and a head, i.e., discharge end pulley 118. A series ofspaced idler rollers 120 supports the belting 114 in a "deep trough"configuration for carrying high loads without spillage. The conveyor 36is illustrated as being powered by a hydraulic motor 122 which turns thehead end pulley 118. The figures depict the belting 114 as having awidth of about 30-36 inches.

Conveyor 36 lifts the shredded materials to an elevation dictated bytransport considerations. Generally, an elevation which provides atransport clearance of about 13.5 feet is considered appropriate. Theconveyor 36 is configured to carry the materials upward at an angle 124of about 18-22 degrees from the horizontal, the maximum angle generallyattainable without backflow or overflow of materials from the belt 114.

The discharge hood 38 at the head end of the primary belt conveyor 36comprises an enclosure for directing conveyed materials downward ontovibrating screen 40 which is immediately below. Such hoods areconveniently used for belt conveyors.

The vibrating screen 40 has a single downwardly sloped deck 126 and isvibrated by a hydraulic or electric motor 128. The screen medium 130 ispreferably of between about 1/2×1/2 inch and 3×3 inch mesh for manyapplications. The screen mesh opening may be varied, depending upon therequirements of the particular application.

In the illustrated embodiment, the screen deck is 8 feet long by 4 feetwide.

In contrast to the screen mounting of other systems, the vibratingscreen 40 is mounted in a reverse configuration so that oversizematerials are moved toward the trailer front 18 rather than the rear,i.e. discharge end 20. In addition, the screen 40 is generally alignedwith the belt conveyor 36, i.e. at an angle of about 18-22 degrees fromthe horizontal. As a result of this configuration, the materials passingthrough the screen 40 may be treated with an additive and be directlyintroduced into the mixer 48 without an intermediate conveyor or hopper,and without exceeding the 13.5 foot height limitation. In addition, thetrailer space taken up by the screen 40, discharge chute 44 and mixer 48is minimized, allowing room for a folding end conveyor 50 of 28 footlength or even greater.

A single deck vibrating screen useful in soil remediation ismanufactured by Portec/Kolberg of Yankton, S. Dak., and may be poweredby either an electrical motor or hydraulic drive.

The vibrating screen 40 has an oversize material discharge end 132 fromwhich oversize materials are ejected onto cross-conveyor 42. Thecross-conveyor 42 has a short belting 134 driven by motor 136. Ifdesired, the cross-conveyor motor 136 may be reversible so that oversizematerial may be discharged from either side of the trailer.

Materials which pass through the screen medium 130 further pass in astream downwardly through the discharge chute 44 which in turn feeds thepug mill mixer 48. The screen 40 is mounted at a height above the mixer48 which permits the front chute wall 138 and rear chute wall 140 tohave sufficiently vertical angles to shed the screened material.

For most applications, the preferred location in the train 12 forintroducing i.e. dosing additives to the process material is within thedischarge chute 44. Exemplary apparatus for accomplishing suchintroduction has been described above. The range of addition rates mayvary widely, depending upon the particular process.

The mixer 48 is a pug mill of the type manufactured by various companiesincluding Portec/Kolberg of Yankton, S. Dak. The mixer 48 is illustratedas a double shaft horizontal flow pugmill which is fed at the front end46. The shafts 142 have attached paddles 152 (see FIG. 5) and are drivenby a diesel engine 144 acting through a belt 148 and a speed reducerdrive 146, as shown in FIG. 1. A fuel tank 150 is shown which suppliesfuel to the engine 144.

The end conveyer 50 has a receiving trough 154 for receiving the mixedprocess materials and additive on the belting 156. The end conveyor 50includes a frame 158, tail end pulley 160, head end pulley 162, head enddrive motor 164, and spaced sets of idler rollers 166. The head end 168of the conveyor folds over forwardly about axis 170 to the travelposition 174 by the action of a pair of hydraulic cylinders 172 actingon pins 176.

The end conveyor 50 is supported at an angle 178 typically about 18-22degrees from the horizontal, by central undercarriage members 180. Whenthe head end 168 is folded upwardly and forwardly, undercarriage member182 becomes disconnected at its lower end and lays against the conveyor50.

The illustrated embodiment uses a fueled engine 144 such as an 80 hpdiesel engine for driving the pug mill mixer 48. The engine 144 alsodrives a hydraulic pump 184 which supplies hydraulic motors driving thebelt feeder 32, shredder 34, conveyors 36, 42 and 50, and vibratingscreen 40. The hydraulic pump 184 also supplies high pressure fluid forthe hydraulic cylinders 98 on the grizzly 28 and the cylinders 172 whichfold the end conveyor 50. The additive pump 52 may also be driven by ahydraulic motor 186.

The conventional hydraulic system includes a fluid reservoir 188 as wellas control valves and conduits directed to each hydraulic motor andcylinder. The fluid conduits and valves are not shown in the figures forthe sake of clarity.

In the illustrated configuration, all equipment is driven by theon-board engine 144. No electrical hook-ups to external power sourcesare required.

Alternatively, some or all of the motor-driven equipment may have anelectrical motor in place of the hydraulic motor. Operation of such aplant will require on-site electrical power. For the purposes of theinvention, any type of motor may be used.

In most cases, the vibrating screen 40 is the factor which limitsthroughput of soil or other material through the plant 10. Thus, a 4foot by 8 foot vibrating screen with a 2-inch opening mesh will permit anominal soil remediation rate of about 100 tons per hour. However, thenominal capacity of a pug mill having an overall length of about 8 feetand a width of 4 feet is greater than 100 tons per hour, and may be upto 300 or more tons per hour, depending upon the materials beingprocessed. This excess capacity results in greater material residencetime in the pug mill, enhancing the degree of mixing.

As indicated in FIGS. 1, 3 and 4, conventional jacks 190 are providedfor stabilization of the trailer 14.

It is anticipated that various changes and modifications may be made inthe construction, arrangement, operation and method of construction ofthe portable unitary screening/dosing/mixing plant disclosed hereinwithout departing from the spirit and scope of the invention as definedin the following claims.

What is claimed is:
 1. A portable unitary screening/dosing/mixing plantfor treating particulate matter, comprising:a transport trailer forover-the-road travel; a screening/dosing/mixing train mounted on thetrailer, said train comprising:a coarse grizzly for receiving saidparticulate matter and removing oversize materials therefrom; a hopperbeneath said grizzly for receiving said grizzly-screened particulatematter through an upper inlet and discharging said grizzly-screenedparticulate matter through a lower outlet; a generally horizontalconveyor belt feeder for receiving and transporting the grizzly passedparticulate matter away from the hopper to a pulverizing shredder; apulverizing shredder for receiving grizzly passed particulate matterfrom the belt feeder, and continuously pulverizing and discharging saidreceived particulate matter; a primary belt conveyor for receiving andconveying said shredded particulate matter to a conveyor discharge hood;a conveyor discharge hood for confining and directing said conveyedshredded particulate matter to a vibrating screen; a vibratingsingle-deck screen mounted for receiving and screening said conveyedshredded particulate matter to remove oversize materials and dischargescreened particulate matter, said screen mounted to move said screenedparticulate matter in a reverse direction; a screen discharge chute forreceiving said particulate matter passing through said screen, and fordischarge thereof to a mixing means; mixing means for receiving andcontinuously mixing screened particulate matter discharged from saidscreen discharge chute, and discharging the mixed particulate matter; anend conveyor for receiving and conveying said discharged mixedparticulate matter to an elevated location for end discharge into atransport vehicle, container, hopper or pile, said end conveyor havingan inlet portion and a discharge portion, said discharge portionfoldable over said inlet portion to a travel position; and means forintroducing an additive material to the particulate matter upstream ofsaid mixing means for intimate contact therewith.
 2. Thescreening/dosing/mixing plant of claim 1, wherein said introducing meanscomprises means for pumping a liquid additive.
 3. Thescreening/dosing/mixing plant of claim 1, wherein said introducing meanscomprises means for pumping a liquid additive at a controllable ratefrom a vessel into said screen discharge chute.
 4. Thescreening/dosing/mixing plant of claim 1, wherein said introducing meanscomprises means for conveying a solid additive.
 5. Thescreening/dosing/mixing plant of claim 1, wherein said introducing meanscomprises means for conveying a solid additive from a container intosaid screen discharge chute at a controlled rate.
 6. Thescreening/dosing/mixing plant of claim 5, wherein said introducing meanscomprises an elongate screw conveyor.
 7. The screening/dosing/mixingplant of claim 1, wherein said end conveyor is configured to dischargesaid mixed particulate matter and additive at an elevation of 8 to 15feet above ground level.
 8. The screening/dosing/mixing plant of claim1, wherein said mixing means is a double shaft pugmill.
 9. Thescreening/dosing/mixing plant of claim 1, wherein said plant isconfigured for the processing of at least 75 tons per hour of saidparticulate matter.
 10. The screening/dosing/mixing plant of claim 1,wherein the overall length, width and height of said plant is configuredfor highway travel without escort vehicle(s).
 11. Thescreening/dosing/mixing plant of claim 10, wherein the overall lengthfrom kingpin to rearmost end is no more than about 53 feet, the width isno more than about 8 feet 5 inches and height is no more than about 13.5feet.
 12. The screening/dosing/mixing plant of claim 1, wherein thevibrating screen is mounted beneath the head end of the primary conveyorin a reverse configuration and generally parallel to the primaryconveyor.
 13. A high rate portable unitary screening/dosing/mixing plantfor soil remediation, comprising:a transport trailer for over-the-roadtravel; a screening/dosing/mixing train mounted on the trailer, saidtrain comprising:a coarse grizzly for receiving contaminated soils andremoving oversize materials therefrom; a hopper beneath said grizzly forreceiving grizzly-screened contaminated soils, said hopper having anupper inlet and a lower outlet; a generally horizontal belt conveyorfeeder for transporting the grizzly-screened soils away from the hopper;a shredder for receiving grizzly-screened soils from the belt conveyorfeeder, and continuously pulverizing and discharging said receivedsoils; a primary belt conveyor for receiving and conveying said shreddedsoils to a conveyor discharge hood; a conveyor discharge hood forconfining and directing said conveyed shredded soils to a vibratingscreen; a vibrating single-deck screen mounted for receiving andscreening said conveyed shredded soils to remove oversize materials anddischarge secondary screened soils, said screen mounted in a reversedirection to move said secondary screened soils in a generally reversedirection; a screen discharge chute for receiving said secondaryscreened soils from said screen, and for discharge thereof to mixermeans; mixing means for receiving and continuously mixing secondaryscreened soils discharged from said secondary hopper, and dischargingthe mixed soils; an end conveyor for receiving and conveying saiddischarged mixed soils from the mixing means to an elevated location forend discharge into a transport vehicle, container, hopper or pile, saidend conveyor having a tail end for receiving mixed soils and a head endfor discharging said mixed soils at an elevated position distant fromthe trailer, said end conveyor upwardly foldable in a middle portionwherein said head end is folded over a tail end portion for transport ofsaid trailer; and means for introducing an additive material to thesoils upstream of said mixing means for intimate contact therewith. 14.The screening/dosing/mixing plant of claim 13, wherein said mixing meansis a double shaft pugmill.
 15. The screening/dosing/mixing plant ofclaim 13, wherein said plant is configured for the processing of atleast 75 tons per hour of said soil.
 16. The screening/dosing/mixingplant of claim 13, wherein the overall length, width and height of saidplant is configured for highway travel without escort vehicle(s). 17.The screening/dosing/mixing plant of claim 16, wherein the overalllength from kingpin to rearmost end is no more than about 53 feet, thewidth is no more than about 8 feet 5 inches and height is no more thanabout 13.5 feet.
 18. The screening/dosing/mixing plant of claim 13,wherein the vibrating screen is mounted beneath the head end of theprimary conveyor in a reverse configuration and generally parallel tothe primary conveyor.